Vitamin D status may indeed be a prognosticator for morbidity and mortality in patients with COVID‐19

To the Editor,

We read with interest the systemic review and meta‐analysis by Munchi et al. ¹ of emerging evidence that vitamin D deficiency is associated with poorer outcomes and prognosis in patients with COVID‐19 and would like to report our experience in the United Kingdom (UK). We recently conducted a prospective cohort study to assess the importance of vitamin D (25‐OH‐D) deficiency in older patients with COVID‐19. ² Our significant findings were that patients with low concentrations of 25‐OH‐D (≤30 nmol/L) demonstrated clinically relevant, elevated markers of cytokine release syndrome and were more likely to become hypoxic and require ventilatory support. Although our study was underpowered to detect a mortality difference between deficient and replete groups, our data support that vitamin D status may be a surrogate prognosticator for morbidity and mortality in patients with COVID‐19.

It is established that there is a complex interplay between vitamin D and various components of the innate and adaptive immune responses to both bacterial and viral infections. Alongside it is anti‐inflammatory properties, vitamin D provides a protective role for alveolar epithelial and endothelial cells and reduces vascular permeability. In addition, vitamin D enhances ACE‐2 expression which is actually favorable against acute lung injury. ³ Whether the link between vitamin D deficiency and requirement of ventilatory support observed in our cohort represents a causal relationship is unclear. However, disruption of one or more of these defensive pathophysiological processes may explain the association.

Mortality and hospitalization rates for COVID‐19 appear higher in northern latitude countries compared to those closer to the equator ⁴ and this supports an interrelation between vitamin D deficiency and adverse prognosis. For special consideration are older adults, particularly those who are institutionalized, who are inherently vulnerable to vitamin D insufficiency because of inadequate sun exposure and dietary imbalance and may have worse outcomes with COVID‐19. In the UK, there is also growing concern that the Black, Asian, and Minority Ethnic community are more susceptible to severe presentations of COVID‐19 as a result of higher skin melanin content and reduced synthesis of vitamin D.

Regardless of the etiology, vitamin D deficiency is readably diagnosable and correctable. On the basis of this reasoning and pending results of trials evaluating vitamin D supplementation and appropriate dosing within the context of COVID‐19, efforts to manage vitamin D deficiency should be encouraged.